The present invention relates to a laser resonator for generating a laser light to cut or weld such hard and rigid materials as metals, ceramics, etc.
It has been popular in recent years to cut or weld metals, ceramics or the like hard materials by an apparatus utilizing laser light of a high energy density.
The structure of a conventional laser resonator used in the above processing apparatus will be explained with reference to FIG. 11.
In FIG. 11 showing the structure of a conventional laser resonator: element 41 is an output mirror through which the laser light is emitted; element 42 is a terminal mirror for reflecting the laser light; element 45 is a main flange; element 46 is a central block; element 47 is a discharge tube; element 48 is an electrode for starting the discharge; element 49 is a copper plate to impress a high frequency current to each electrode; element 50 is a matching circuit network of the high frequency current; element 51 is a coaxial cable; element 52 is an RF power source; element 53 is a piping; element 54 is a heat exchanger; element 55 is a mechanical booster pump; element 56 is a filter; element 57 is an orifice; element 58 is a regulator; element 59 is a PFA pipe; element 60 is a gas pressure regulating unit; element 61 is a vacuum pump (oil rotary pump); element 62 is an integrating sphere; element 63 is a photodetector.
The resonating ratio of the output mirror 41 and the terminal mirror 42 is controlled by respective adjusting bases 43 and 44.
The operation of the conventional laser resonator constituted as above is described.
The output mirror 41 and the terminal mirror 42 which are placed at both ends of one or a group of a plurality of discharge tubes 47 are supported by the respective bases 43 and 44. The angles of the mirrors 41 and 42 are adjusted so that the optical axes are parallel to the discharge tubes 47. In an optical oscillator thus formed, the power from the RF power source 52 is sent, via the coaxial cable 51, to the matching circuit network 50, where the power is converted to the conjugate complex impedance of the impedance of the discharge tubes 47. The RF power is transmitted through the copper plate 49 to the electrodes 48, with initiating the discharge of the discharge tubes 47. The piping 53 connected to the optical oscillator constitutes a vacuum container together with the main flange 45 and the central block 46. The laser gas is circulated within the vacuum container by the mechanical booster pump 55. The heat exchanger 54 is provided in the middle of the piping 53 so as to remove both the compression heat generated by the mechanical booster pump 55 and the heat resulting from the discharge of the discharge tubes 47. The laser light obtained by the discharge of the discharge tubes 47 is partly emitted through the output mirror 41 to be used to cut metallic or ceramic materials.
In this case, since a part of the laser gas is dissolved when the discharge tubes 47 operate, it is necessary always to supply fresh laser gas to the discharge tubes 47. The fresh laser gas is supplied from the vicinity of the output mirror 41 to the optical oscillator through the PFA piping 59. At this time, the gas pressure is reduced by the regulator 58, and the flow rate is controlled by the orifice 57, and moreover the contaminant is removed by the filter 56. Meanwhile, the exhaust system is connected at the sucking side of the mechanical booster pump 55 to the vacuum pump 61 via the gas pressure regulating unit 60.
Apart from the laser light emitted through the output mirror 41, a part of the laser light is output from the terminal mirror 42. After the intensity of the laser light is attenuated by the integrating sphere 62, the laser light is introduced into the photodetector 63. This laser light is utilized for the purpose of monitoring, feed-back or diagnosis in the form of output signals of the photodetector 63.
In the meantime, Japanese Laid-Open Patent Publication No. 3-231482 discloses the arrangement to measure the intensity of the laser light output from a laser resonator thereby to feedback the laser output.
In the prior art as above, the integrating sphere 62 is always required so as to monitor the laser light projected from the terminal mirror 42. Therefore, it is disadvantageous that the optical axis of the integrating sphere 62 is necessary to be adjusted at the mounting time of the integrating sphere 62, and the reflectivity of the reflecting surface of the integrating sphere 62 is changed with time due to temperature changes, which results in the deterioration of the monitoring accuracy.
Moreover, since and when the burning pattern of acrylic acid or the like should be collected in order to adjust the transverse mode of the laser light in the prior art, the resultant gas is harmful to human bodies and it is necessary to discharge the gas after a special treatment.